Stators are made of a plurality of steel sheets slightly insulated from one another (laminated structure) and defining an annular shape with a stator bore into which the rotor is housed.
Axial slots open in the stator bore to house stator conductors. The stator conductors include a copper bar with an insulation that is very sensitive to the temperature, such that when the temperature increases above a predefined value, the insulation properties fall.
The laminated structure prevents eddy current circulation and thus generation of hot spots that, during operation, could damage the stator conductor insulation.
Thus, possible damages to the laminated structure that can cause two or more steel sheets to be short circuited must be removed. For example such damages can occur during maintenance operations when extracting the rotor from the stator bore or because a tool falls within the stator bore.
The stator has a central part with the stator bore that is substantially cylindrical, and end parts with the stator bore having a step conical shape.
When the step conical shaped end parts are damaged, the steel sheets of the damaged step conical shaped end part are un-stacked and then re-stacked (the damaged steel sheets are naturally replaced or repaired).
Un-stacking and re-stacking the steel sheets is very time consuming such that the time required for these operations could not fit into the conventional maintenance plan. For example time is required for the un-stacking and re-stacking operations, supplying the spare parts, execution of repairs.